1. Field of the Invention
This invention pertains to insulating materials, and more particularly to insulating materials that increase the comfort of sleeping persons.
2. Description of the Prior Art
It is well known that the body heat of a sleeping person is readily transferred to the water of a water mattress if the water is not kept at a fairly high temperature. Especially in older people, the danger of hypothermia is acute. Since the body temperature usually remains about 98.degree.-99.degree., it is necessary that the water temperature be about 80.degree.-85.degree., depending upon the comfort range of the individual person. If the room ambient temperature is normally 70.degree.-75.degree., the water must be heated, usually by an electrical heater under thermostatic control, to the desired temperature. Because of the mass of the water, its temperature cannot be changed quickly. Thus, the heater is usually left on during daytime hours as well as at night. The resulting usage of electrical energy is costly. The control and heater have limited useful lives, thus requiring the eventual expense of replacement. Moreover, the inherent physical comfort of a waterbed can be counterbalanced by the anxiety of some people over sleeping on an electrical appliance. Similar anxieties are frequently present regarding electric blankets.
To eliminate the problems encountered with electrically heated bedding material, attention has turned to providing coverings and mattress pads with increased insulation properties. For example, U.S. Pat. No. 2,596,547 illustrates a bed cover containing a number of relatively small sewn pockets into which can be inserted formed pads of insulating material such as wool, kapok, or down. The insulating pads can be removed when required for laundering the bed cover. It will be apparent that the sewn construction of the pockets of the 2,596,547 patent is expensive. Further, it is a laborious and time consuming chore to remove and insert the numerous small pads of insulating material into the pockets. Other designs of pocketed bedding material, although not necessarily for insulating purposes, are shown in U.S. Pat. Nos. 2,576,455, and 2,614,273.
Another heat related development in bedding materials is the utilization of the heat reflecting properties of metal foil. In the past, the primary function of the foil has been to decrease the danger to people who smoke in bed, i.e., the concern has been with creating fireproof mattress covers and pads, as exemplified by U.S. Pat. Nos. 2,801,427 and 3,818,520. While the metal foil serves admirably in reflecting heat, the previous mattress pads incorporate the foil as a permanent part of the pad, thus precluding washing or altering the pad.
When a person moves on the surface of a waterbed, the water within flows from a high pressure region to a low pressure region. This produces the so-called "wave effect", and a second person on the bed may be bounced until the water pressure is equalized. Closely related to the wave effect is the "sinking effect", which is concerned with the amount a person will sink into the water mattress. Since ordinary mattress pads and sheets are quite flexible, they offer little or no assistance in preventing the sinking effect. Some waterbeds are equipped with internal baffles to damp the wave effect. Over filling the mattress or adding thickening agents to the water have been attempted. However, internal baffles are expensive, and water thickening agents make draining the waterbed difficult.
Thus a need exists for an insulated mattress pad that is low in cost, easy to use and launder, and that provides more comfortable sleeping in a waterbed than was previously possible.